BLOOD VESSELS OF THE BRAIN 387 



artery, and as it passes along the longitudinal fissure, between 

 the hemispheres, it lies close to its fellow of the opposite side. 

 Numerous branches proceed from each anterior cerebral artery : 

 Basal or central { Antero-medial. 

 ( Medial orbital. 

 r , . , J Anterior medial frontal. 



I Intermediate medial frontal. 

 I Posterior medial frontal. 



The ant ero -medial arteries pierce the base of the brain anterior to the 

 optic chiasma. They supply the rostrum of the corpus callosum, the 

 lamina terminalis, and the septum pellncidum. 



The cortical branches supply the greater part of the 

 medial surface of the hemisphere and parts of the orbital 

 and supero-lateral surfaces (Figs. 146, 147, 148). 



The medial orbital branches are two or three in number. They turn 

 round the margin of the longitudinal fissure to reach the medial part of the 

 orbital surface of the frontal lobe. They supply the gyrus rectus, the olfactory 

 tract and bulb, and the medial orbital gyrus (Figs. 146 and 147). 



The anterior medial frontal artery ramifies upon the anterior part of the 

 medial surface of the frontal lobe, and its terminal twigs turn round the 

 upper margin of the cerebral hemisphere, and supply the upper part of the 

 supero-lateral surface of the frontal lobe (Fig. 146). 



The intermediate medial frontal artery ramifies on the medial surface 

 of the frontal lobe posterior to the preceding branch. Its terminal part 

 passes over the paracentral lobule, and reaches the adjacent portion of the 

 supero-lateral surface of the cerebral hemisphere (Figs. 146, 148). 



The posterior medial frontal artery ramifies on the medial surface of 

 the prsecuneus, and its terminal twigs turn round the upper margin of 

 the cerebral hemisphere to gain the supero-lateral surface. 



Arterise Cerebri Mediae. At first each middle cerebral 

 artery passes laterally, along the stem of the lateral fiss-ure, 

 and then upwards in the lateral fossa, where, on the surface 

 of the insula, it breaks up into a number of large terminal 

 branches. Before the posterior ramus of the lateral fissure 

 is opened up to expose the insula in the lateral fossa, the 

 terminal branches may be seen emerging from between its 

 two lips (Fig. 148). Then they diverge and supply a wide 

 area of cortex on the supero-lateral surface of the hemisphere. 



The branches which spring from each middle cerebral 

 artery may be classified as follows : 



Lateral orbital. 

 Inferior lateral frontal. 

 Ascending frontal. 

 Cortical branches. parieta] { Ascending parietal< 



Parieto-temporal. 

 Temporal. 



